The present invention relates to apparatus having a pair of overlapping blades for cutting partially through one or more layers of material surrounding an elongated, filamentary member, and then severing the material at the position of the cuts by moving the blades axially of the member while restraining the latter against axial movement, or by maintaining the blades stationary and moving the member axially with respect thereto. More specifically, the invention relates to novel configurations and arrangements of the blades used in apparatus of the foregoing type to provide improved operation, particularly when operating upon members of relatively large diameter.
The prior art contains many examples of manually, semi-automatically and automatically operated apparatus for severing layers of material which cover elongated, filamentary members for the purpose of exposing an end portion or intermediate part of such member. In one widely used application, a layer of insulation is cut, severed and stripped from a free end of an electrical wire. Such apparatus is also used for removing coating layers from selected portions of optical fibers, coaxial cable, flat ribbon cable, etc. Although it will be understood that the present invention is suitable for use in all analogous operations, it will be explained and hereinafter referred to in the context of severing and stripping a single layer of insulating material from a free end portion of an electrical wire.
While some severing and stripping apparatus has used only a single cutting blade which is moved around the wire, it is far more common to employ a plurality of blades to cut the insulation. In any case, the blade or blades are mounted for reciprocating movement of the cutting edge(s) radially of the wire or other elongated member. When two or more blades are used in such operations, they may be mounted with the cutting edges in direct opposition, i.e., in the same plane perpendicular to the axis of the wire, such as in the various embodiments of cutting and stripping apparatus disclosed in U.S. Pat. Nos. 4,993,147 and 4,993,287, both issued Feb. 19, 1991 and assigned to applicants' assignee. Since at least portions of the opposing edges of blades mounted in this manner are in mutual, abutting relation when the blades are moved toward one another to the limit of their movement, they will be termed "abutting blades."
In some apparatus of this type, it has been found convenient to mount the blades with opposing surface portions in superposed, sliding contact as the blades are moved reciprocally relative to one another and radially of a wire positioned therebetween with its axis perpendicular to the blade cutting edges. The prior art includes numerous examples of cutting and stripping apparatus with blades arranged in this manner. Since portions of such blades are in mutually overlapping relation, they are termed "overlapping blades, " as distinguished from abutting blades The cutting edges of overlapping blades are usually formed along the edges of notches, e.g., of V-shaped configuration, in one side of the blades.
The cutting edges of both types of blades are normally formed at the juncture of two essentially planar surface portions meeting at an acute angle to form a sharp edge. The plane of at least one of the planar surfaces forming the cutting edge(s) also intersects the axis of the wire at an acute angle, the other planar portion commonly being perpendicular to the wire axis; the planar portion(s) adjacent the cutting edge(s) arranged at an acute angle to the wire axis are herein termed "bevel surface(s)."
After the blade cutting edges are moved toward one another to cut at least partially through the insulation, the blades and wire are moved relative to one another in a direction axially of the wire to complete the severing of a slug of insulation and strip it fully or partially from the conductor. The slug may be stripped in one of two ways: 1. the wire may be firmly clamped at a position on the side of the blades opposite the slug to be stripped and the blades, while engaged with the insulation, moved simultaneously in the direction of the slug, or 2. the wire may be grasped mechanically or manually on the side of the blades opposite the slug to be removed and moved axially as the engaged blades remain stationary.
Although blades of the abutting type have been arranged with the planar surface portions adjacent the cutting edges and facing the slug to be stripped disposed at the same angle to the axis of the wire, conventional wisdom dictates that, when employing a pair of overlapping blades, the bevel surfaces face in opposite directions from the surfaces in sliding contact. This is because such an arrangement places the sharp, cutting edges as closely as possible to the same plane, i.e., the planes of the blade surfaces which are in sliding contact. This may be, and normally is, achieved by employing two identically formed blades placed in front-to-rear surface contact with the cutting edges facing in opposite directions. That is, when identical blades are placed side by side, with the cutting edges facing in the same direction, both bevels extend from blade surfaces facing in the same direction. When one blade is turned over onto its opposite surface and turned end-for-end to place the cutting edges in opposed relation, the bevel surfaces are then on opposite sides of the blades, i.e., on the front surface of one blade and the rear surface of the other.
When overlapping blades with cutting edges in opposed notches are used to cut the insulation on wires of various diameters, the cuts are necessarily incomplete. For example, when a pair of V-shaped cutting edges are employed, the insulation will be cut from four, linear sides, and since the wire is round in cross section and cannot be contacted by the blades, portions of the insulation will remain uncut, assuming neither the blades nor the wire is rotated. Severing of the insulation is completed by relative movement of the blades and the wire in one of the two previously described ways. A slug of insulation is thus severed and moved axially on the wire to be stripped either fully or partly, depending on the distance of blade travel, from the free end of the wire.
When such apparatus, having overlapping, non-rotating blades, is used to cut partially through the insulation and complete the severing thereof by moving the blades to break the uncut portions, the wire is sometimes nicked or scraped by the blades. This problem is generally amplified as the diameter or gauge of the wire increases, with corresponding increase in the axial force exerted by the blades on the slug of insulation being stripped. With common types of insulation, the problem of nicking, etc., requiring scrapping of the wire, is most prevalent in wires of 10 gauge or larger. However, when severing insulation or other coating materials having relatively high tensile strengths, the problem may also arise with smaller gauge wires.
The principal object of the present invention is to provide apparatus and methods utilizing overlapping blades to cut partially through one or more layers of coating material on a filamentary member and severing the material by relative movement of the engaged cutting blades and the member in a manner which greatly reduces or eliminates the tendency of the blades to nick or score the member during the severing and/or stripping operation.
Another object is to provide apparatus for and methods of severing and stripping insulation from an electrical wire, or the like, including configuring and relatively positioning a pair of overlapping blades in a novel manner to improve operation and reduce scrap.
Other objects will in part be obvious and will in part appear hereinafter.